Process of making ornamental mirrors



April 21, 1931- G.V F. coLsERT ET AL PROCESS OF MAKING O RNAMENTAL MIRRORS Filed April 1s INVENTORS i. Patented Apr. 21, 1931 Unirse stares rATENr ortica GEORGE F. COLBERT AN D WILLIAM H. COILBERT, F PITTSBURGH, PENEl'SYIN'AIiI'IA,` AS- SIGNORS TO LIBERTY MIRROR WORKS, A CORPORATION OF PENNSYLVANIA vzo PROCESS OF `IBzIALKIN'G- ORNAMENTAL MIRRORS Application filed April 16,

y The invention relates to a process of making multi-tone ornamental mirrors similar to those shown and described in our copending application, Serial Number 340,378. The invention has for its object the provision of a method for producing mirrors of this type in a better and cheaper manner. A further object is to provide a method which can be practiced to produce these mirrors rapidly and with the exercise of a much less degree of skill.

In the practice of the process set forth in our previous application, theportions of the metallic lm first applied to the glass, which required removal to form the pattern or' picture, were removed by mechanical means involving cutting, scraping and brushing or the like; while in the practice of the present invention, these mechanical manipulations are all avoided, and theproduction of the required design is accomplished by the use of solvents; the basic coating being so prepared or treated that only parts thereof are acted on by the solvent, thus leaving the remainder of this coating in the form of the requisite pattern. rlhe term solvent is used throughout in its broad sense to designate any compound which is eective to remove or dissolve certain unprotected portions of the hlm by chemical reaction therewith or otherwise. A. mirror made in accordance with the proc-Y ess and certain steps in theprocedure are illustrated in the accompanying drawings, wherein: v Figure 'l is a face view of the mirror. Fig. 2 is a section on the line II-II of Fig. 1, the

`films of'material shown in this gure (and Figs. 3 to 5) being much exaggerated in thickness for the purpose of clear illustration. And Figs. 3 to 5 illustrate steps in the process.

Referring to the drawings, 1 is a sheet of transparent material, such as glass, 2 is a precipitated film', .preferably of a white metal, such as silver or mercury, which covers the main body portion ofrone surface of the glass, and 3 is arecipitated film of a metal or metal compoun such as lead sulphide; which presents the desired contrast in color to that of the lm 2. The two lms are so disposed, as to give an ornamental design, such as is indi-l 1929. Serial No. 355,507.

.portantonea Other materials which maybe employed are gold and silver or mercury, gold and lead sulphide, copper and silver or mercury, and copper and lead su phides, or combinations of such elements, and their chemical compounds, with certain organic substances.

In carrying out the process toV make the particular mirror herein shown, the glass is placed in a horizontal position and its upper surfaceis covered with ,a solution containing alead salt which is precipitated, as a film of lead sulphide, over the entire surface ;the procedure followed, preferably that set forth in our Patent No., 1,662,565. This ilm is then thoroughly cleaned by washing in water, and is immediately coated with an emulsion sensitive to light (Fig. 3), such, for' example, as the socalled cold top enamel well-known in the photo engraving art. The desired design ,or picture is then impressed on the sensitized surface either by direct contact printing from a photographic negative, lor by the projection of an illuminated image thereon, or by covering the surface with alstencil plate, vcut to the required pattern; and after ,the necessary exposure to light-which varies with thel intensity of the illumination used-the latent image is developed in such a manner that the light treated portions of the enamel emulsion are rendered insoluble; the details of such treatment being well known to those skilled in this art. The plate is then rinsed in water which removes the portions of the lm which have not been exposed to the light (Fig. 4:) after which the plate is dried. The plate now has on its rear side the patterned ortions ofthe enamel covered lm which it is desired to retainin the finished mirror.

The plate, with the metallic film up, is now placed in a. tray co taining a dilute solution in matter of detail, being (e. g. about of nitric acid. This removes all of the metallic lm exce t the part 3 which is protected by the insolu le enamel coating (Fig. 5). The plate is then immediately washed with water to prevent the nitric acid from attacking and in]uring the l enamel film.

exaggerated in thickness, or the purpose of illustration, the combined thickness of the three films shown in Fig. 2, for instance, not being appreciably greaterr than that of the single film 2.

It is also possible to produce the desired multitone effect by depositin the silver film, instead of the lead sulphide lm, as the first step of the process; but this is n'ot productive of .as satisfactory results as t e procedure first described, since in the application of a lead sulphide film over silver, the sulphide film tendsto work under the edges of the protected silver areas and lblur, or 1mpair the shar ness of, the boundary lines.

If it is desired to produce a silver mirror having certain areas covered b painter lacquer, this may be accomplishe by first coating the entire plate with silver, then coating the silver film with the cold to the esired desi then developing and removing the solu le portions ofthe enamel,

-out in either of two ways.

and then removing the uncoated portions of the silver film with a solution of vnitric acid ;-after which any desired color of paint or enamel may -be applied to the entire area of the surface as treated.

In order touse gold as the first film,-in producing a gold and silver composite,.-it is desirable to precipitate a lead sulphide film over the entire gold film, as the lead sulphide gives a strong enduring protection of the gold coat which can, under these circumstances, be made usually relatively thin ;-this being the most satisfactory methof of reinforcing the gold film when a onetone gold mirror is to be produced. Afterv thus protecting 'the gold coating with the lead sulphide coat, the procedure follows that already described in the 'production of the mirror of Figs. 1 and 2, except that a dilute solution (about a 10% solutlon) of aqua regia is used in place of nitric acid. y

It is also possible to practice the process 'by a print-ing method, which may be carried In the rst of these methods one lentire surface of the plate is coated with one of the desired metallic enamel films, and then carefully cleaned bywashing. The freshly cleaned metallic film is zinc--and the required pattern is 1m ressedv on the sensitized surface by the usua printing and developing process, which leaves the design in raised relief. The developed surface is now inked up with a leather roller which shows up on portions of the film that have been exposed to the light, and is next covered with dragon blood (a red resinous powder which, when melted, becomes any acid resist) and heated. The plate is then immersed in water and by careful swabbing with soft cotton all' the unprinted portions are rubbed away, leaving only the desired design which is covered and, rotected by the ink. After this treatment t e plate is thoroughly dried, and then immersed in a dilute an etched or cut printing plate), and then air dry the plate until the inked pattern is completely set. We then place the plate in a di ute acid solution to remove the portion, not protected b the attern, and proceed as in the first met od a ve described. A further modification of this procedure is the use of a protecting attern in the form of a stencil in place o the ink pattern, such stencil being pasted in place and composed of acid resistin material.

yThe process '1s also applicable in the production of mirrors in which a portion of the metallic coat must be removed to provide a clear area for the application of a print, legend, photo aph, or the like, or to make visible some o ject behind the mirror, such as the face of 'a clock, which clock may be secured to the back of the glass sheet. In such case the process, as heretofore described, is `followed up to, and including, the step of removing the unprotected portion of the metallic film with the acid, after which the clear lio :to such action, a

` moans tion of light, developing saidexposed por- Ypattern so that oneart of tions'to forma the coating-is su ject to the action o a solvent and the remaining part is not subject lying solvent to remove the soluble part o t e coatin and the underlying parts of ysaid film, an then applying ective article, which consists in covering' the a backing of a color contrasting to t atlo said film over the entire surface of the sheet carrying said film.

2. A process of forming a decorative reface of a trans arent glass sheet with a metallic film precipitated from a solution, coating said lm with a photo-sensitive emulsion,

exposing portions of said coating` to the action of light, developing said exposed portions to form a pattern =so thatA one art of the coating is subject to the action o a solvent and the remaining part is not subject to such action, a plying solvent to remove the soluble part o the coatingI and the underlying parts of said film, and then depositing 

